Telephone system



v. s. THARP TELEPHONE SYSTEM Filed Sept. 22. 1926 MY m? M QT Dec. 3, 1929.

Iru ren Ur 135?" 5, Th app Mi TJMFIL RAN Patented Dec. 3, 1929 UNITED STATES nsets PATENT OFFICE VICTOR S. THARP, 0F ELMHURST, ILLINOIS, ASSIGNOR TO AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION 013 DELAVJAEE TELEPHONE SYSTEM Application filed September 22, 1926.

This invention pertains to automatic telephone systems in general, but is more particularly concerned with telephone systems in which calls to dead or temporarily-interrupted-service numbers are automatically eX- tended to an intercepting operator. The object of the invention is the provision of a new and improved trunk circuit for the trunk over which calls to dead or temporarily-interrupted-service numbers are automatically trunked to an intercepting operator without causing the registration of the call on the calling subscribers meter.

In the ordinary course of events in the extension of a call from a calling to a called subscriber, one or more switches are operated, the last switch being a connector, for 6X21111- plc a Strowger vertical and rotary type connector, and when the called subscriber answers the call, a bridge is placed across the called line which causes the operation of a ring-cut-ofi relay in the connector to cut off the ring and complete the connection, and also causes the operation of a back-bridge relay, the latter relay functioning to reverse the normal current flow over the calling lineto operate the calling subsoribers meter. Then a call is trunked to an intercepting operator and the call is answered by the intercepting operator, means must be provided to operate the ring-cutoff relay in the connector switch to cut oil theaing and complete the talking connection, yet prevent the operation of the back-bridge relay in order to prevent the registration of the call on the calling subscribers meter, since it is ordinarily not desired to charge a subscriber for an intercepted call.

The object of the invention and the new features accoi'nplished will be described in detail in the following specification with this aid of the annexed drawing, which shows by means of the usual schematic circuit diagrams the new and improved intercepting trunk circuit together with sufl'icient of the associated apparatus to enable the invention to be clearly explained and its utility appreciated.

Referring to the drawing, the frequency selecting connector FS is one. of a group of Serial No. 136,925.

frequency selecting connectors for extending connections to party lines,'such as the party line comprising conductors 21 and 22. The connector ITS is of the well known Strowger vertical and rotary type like that shown and described in detail in the Patent No. 1,6063%, granted to Arthur J. Bay, November 9, 1926. In the drawing only those elements of the connector FS are shown that are particularly concerned with the present invention.

The connector G is one 01": a group of individual line connectors for extending connections to individual lines, such as the line comprising conductors 21 and 22. This connector is also of the well known Strowger vertical and rotary type like that shown and described in detail in Patent No. 1,580,490 granted to Emil Jacobson April 13, 1926. Only those elements which are particularly concerned with this invention are shown in the drawing.

At the distributing frame DF, the terminals 17 and 18, connected to connector bank contacts 15 and 16, respectively, and the terminals 19 and 20, terminating the party line comprising conductors 21 and 22, are cross connected by means of jumpers 23 and 24. A connection may thus be established with any one of the parties on the party line, comprising conductors 21 and 22, by operating a frequency selecting connector, such as connector FS, to connect with bank contacts 15 and 16, or contacts multiply connected therewith. Similarly, at the istributing frame DF, terminals 17 and 18 connected to bank contacts 15 and 16 respectively, and terminals 19 and 20 terminating the individual line comprising conductors 21 and 22, are normally cross connected by means of jumpers, so that connections with this line ordinarily may be established by operating a connector, such as connector C, to engage the bank contacts 15 and 16, or contacts multi ply connected therewith.

The subscribers substations A A inclusive, A being shownin full, and the others being indicated by showing the bells only, are of the usual automatic type, having their ringers connected from either one or the other side of the line to ground. The substation A is identical to the substation A except that its ring-er is bridged directly across I the line.

The reference character 0 indicates an intercepting operators cord circuit. Since this forms no particular part of the invention, only the sleeve relay connections and the.sec-

tions of the talkin conductors terminating this invention and'will be described in detail hereinafter.

Multiply connected to this intercepting trunk a'r'e tra'fiic ringers, such as traflio ringers TR'rand' TR. .Ea'ch trafiic ringer comprisesfa frequency relay which responds only to Ca particular frequency of ringing current, and a'swit'ching relay with connections as shown.

Under ordinary conditions when service is being extended to all ten substations on the party line comprising conductors 21 and 22, neaconnection is :inade from this line to a traflic ringer. .In the present case, however, it is assumed "that service to .one of the substations on this line, substation A is temporarily interrupted,a' nd that the conductors leading tosub-station A from the partyline conductors 21 and :22 have been disconnected. For .ithis reason, at the distributing frame DF, the terminals 27 and 28 connected to the trafiic ringer TR, are cross-connected to terininals 17 and I81by means of jumpers 2'5 and 26, assuming that the frequency relay" 32 "of traffic ringer vTR is connected to the same side of .the line to which the ringer atrsubstation A is ordinarily connected and responds to the same :frequency of ringing current. Now calls to'sub'station A 'will automatically be'extendedito an intereeptingop- Yerator as willbe described in detail hereinafter. Under ordinary conditionswhen service is extended to substation A, jumpers connecting terminal '17 with terminal '19, and terminal 18 withterminal20" are supplied. Itis assumed in this case, however, thatlxserviceto theisuhst'ation A is temporarily interrupted, and that, "as shown, terminals'l'li I and I8 are connected to terminals 27 and 28:,respectively, assuming that frer qiieney relay;i32",connected across the line,

respondszto the same i'fre'quendy of ringing current the :ringer. at substation A Aigain, :ias :in thefahove'case,"= calls i attempted with substation A will automatically be trunkedao ,the intercepting operator as will be -describedhereinafter., H

- With thisigeneriflidescriptibn'iof the object oft-liegiiivention-and of the apparatus shown in 'lthe {drawing "in mind,a detail description of the operation of the apparatus will now be given. For this purpose it will first be assumed that some subscriber either inadvertently dials the number of the substation A or dials this number to obtain connection therewith not knowing that service thereto is temporarily interrupted. Responsive t0 the digits dialled by the calling subscriber, automatic switches are operated, each switch extending the connection to a succeeding switch, the final switch operated being a frequency selecting connector, which in this case will be assumed is the frequency selecting connector FS. This switch operates responsive to the first two of the last three digits of the called number to position its wipers 13 and 14 in engagement with bank contacts 15 and 16 connected to the party line comprising conductors 21 and 22, and operates responsive to the last digit dialed to position the frequency selecting wipers 5 and 6 in engagement with the contacts 11 and 12 respectively, thereby selecting the frequency of ringing current and the side of the line to which it is to be applied, which would ordinarily operate the ringer at substation A".

Atthe completion of the dialling of the number, operations take place in the frequency selecting connector FS (described in detail in the above referred to reference concerning the operations of this connector) at the completion of which a circuit may be traced from the battery superimposed generator G or direct battery, bank cont-a ct 11, wiper 5, resting contact and armature 9, wiper 18,banli-contact 15, terminal 17, and then over two paths, one path including jumper 23, terminal "19, party line conductor 21, through the'ringers connected to this side of the line to ground, the other path including jumper 25, terminal 27, through the winding of frequency relay 32 to ground. As has been stated, the substation A is disconnected'from the party line; and the other ringers connected to conductor 21 are tuned so as not to respondtothe frequency of ringing current supplied by generator G, the particular genorator now being used. As frequency relay 32,however, is tuned to respond to ringing current from'the generator G, this relay operates As soon as armature 36 engages its working contact, a circuit is established which may be traced from ground by way of armature 57 and the resting contact, armature 0 andithe restingcontact,'conductor 72, armature Strand the workinc contact, through the upper winding-of switching relay 31 to bat.-

tery. Relay 31 operates-and closes a lockingcircuit for itself 'at arl'nature 3 1 which maybe vtraced from ground byway of the normally closed contacts controlled by ar1natur-e '59, resting. contact and armature 67, through the winding of impulse control relay 52, conductor '73, armature 34 and the work mg contact, through the lower winding of relay 31 to battery. By the actuation of armatures 33 and 35, the connection is ertended to the intercepting trunk comprising conductors 717-i, inclusive. Relay 52 ener- 'izes over the above traced circuit and by the disengagement of armature 6O .irom its resting contact, ground potential is removed from conductor 72 to prevent another con nection from being extended to this particular intercepting trunk at this time, and by the engagement of armature with its worlcing contact, a circuit is closed for the impulse relay 5%. Relay 54 operates and prepares the impulse circuit at arn'iature 64;, and at armature 65 closes the circuit for the bridge control relay 53. Relay 53 operates and closes another point in the impulse circuit at armature 62, closes the circuit for the call lamp L at armature 61, and at armature 63 opens a point in the circuit of switch-- inn; relay The lighting of the lamp L indicates to the intercepting operator that a call has been extended over the trunk terminating in the jack J, in response to which she inserts the plug of an idle cord, plug P of the cord O, for example, into the jack il Inserting the plug Pinto the jack J closes the circuit for the sleeve relay 51 in series with the sleeve relay oi"- the cord 0. Relay 51 operates and at armature 59 excludes relay 52 from the holding; circuit of relay 31 of the traffic ringer TR; at armature 58 prepares the circuit for the switching relay 55; and by the disengagement of armature 57 from its resting contact opens the circuit of relay 54 and of the call lamp L, and by the engagement of this armature with its working contact places ground potential by way of working contact and armature 64, working); contact and armature 62, to the midpoint of the bridge across the conductors 74: and 71 which includes the windings of impedance 56 and the resistances R and R. The application of ground potential to the midpoint of this bridge has no utility in this particular connection.

Shortly after the interruption of its cir cuit, relay 54: deenergizes and at armature opens a circuit of relay 53, and by the re lease of ari'nature ('34 ground. potential from the midpoint of the bridge including the resistances ll. and It and the windings of im pedance 56 is removed, and battery potential through the protective resi tance R subituted therefor. A circuit may now be traced from battery, resistance R resting contact and armature 64., working contact and armature 62, resistance R, lower windof impedance 56, conductor '54, armature 35 and the working contact, juniper 26,banl: contact 16, wiper 14, resting; contact and armature 10, wiper 6, bank contact 12, through the lower winding of the ring); (ill-(Til relay 1 to ground. The ring cut-oil relay 4: operates over this circuit and at arinatures 9 and 10 disconnects the ringing circuit and bridges the windings of the back-bridge rclay 2 across the talking conductors. The relay 2 is prevented from operating by reason of the following: After the operation of relay 4, the upper winding of relay 2 short circuited by reas battery potential bein connected to the midpoint of the bridge across conductors 71 and 74, and relay 2 is insuiiiciently energized over its lower winding by reason oi. the resistance R to effect its operation. Shortly after its circuit is opened, relay 53 releases its armatures, closing the circuit for switching relay 55 at armature 63 and disconnecting battery potential from the midpoint of the bridge across conductors 71 and 7-11: at armature 62. The short circuit is now removed from the upper winding of the baclnbridge relay 2 but the closed circuit now including both windings of the back-bridge relay 2 and both windings of the impedance 56 and resistances R and R, has practically twice the resistance as the previous c' cuit which included only the lower winding of back-hi1 c relay 2,. and resistance R and the lower winding of ii pedance 56. Therefore the magneto moe force produced by current in both the windings oi the back-bridge relay is not materially changed and the relay remains deactuated. Consequently, since the backbridge relay 2 is not operated, the normal current flow over the calling line supplied through the windings of the line relay 3 is not reversed and the subscribers meter (not shown) is not operated.

Shortly after its circuit is closer switching; relay 55 operates and at armatures G6 and 68 completes the talking connection from the calling subscriber to the intercep ing; operator w 10, after conn-icting her head set (not shown.) across the talking; combs-tors o the cord in known manner, informs the calli subscriber that service to the substation A is temporarily interrupted or {fives other information as she may have to give the callinp; subscriber concerning the subscriber at substation A. The calling subscriber will then replace his receiver, initiating the release of the operated switches in the well known manner, and the lDlZGlCGlJillllQ' operator will remove the plug P from the jack J.

Removing; the plug P from the jack J opens the circuit of the sleeve relay 51 which deenernizes and releases its armatures. By the release of armature 59, the circiiit oi switching relay 31 of the trailic ringer TB is opened, which thereupon deenergizes and restores its armatures to normal. By the re lease or armature 58, the circuit of relay is opened. Relay 55 retains its armatures operated for an interval to allow for the re lease of relay 81 so that the holding circuit of relay 31 is not restored by the release oi.

armature 67. After the lapse of the interval,

relay restores its armatures to normal.

It is obvious from the foregoing descriptions that if service to any other of the parties a on the party line comprising conductors 21 and 22 also be temporarily interrupted, another set of? jumpers similar to jumpers 2-5 and 26 wouldbe connected from terminals 17 and 18 to the terminals of another traffic ringer, Whose frequency relay was tuned to respond to the same frequency of ringing current as the ringer at that substation, and was connected to the same side of the line. The dialling of the number of that substation by some calling subscriber would again result in the establishment of a connection to the intercepting operator,

It is also evident that it is immaterial to what side of the line the cut-off winding of the ring cut-oil relay 4 is connected (being connected to the lower conductor via wiper 6 when a substation Whose ringer is connected to one conductor of a party line is to be sig- 'na'lled, and to the upper conductor via wiper 5 when a subscriber whose ringer is connected to the other conductor of the party line is to be signalled), the operation being the same in either case. In one case the circuit 'for energizing the cut-off winding ex tends from the midpoint of the bridge across the conductors 71 and 74 over resistance R, the lower winding of the impedance 56, and in the other case, over resistance R and the upper winding of the impedance 56 and conductor 71.

It will be recalled that included in the op oration's performed in the above connection, aground potential was momentarily applied to the midpoint ofthebridge across conductors 71 and 74, which operation had no function in the setting up of that connection. To describe the utility of this operation in the trunk circuit TC, it will be assumed that calling subscriber either inadvertently dials the number of the substation A or dials the number'o'f'th'e subsc iiber at substation A not knowing that service thereto has been temporarily interrupted Responsive to the diallin'goi the digits of this number, a connection is established from the calling subscriber by Way 'ofone or more automatic switches, the last OfrthGSG switches, it will be assumed, is the connector C which operates responsive to the dialling oi the last two digits of the number to position its wipers 13' and 1-4; in engagement with the bank contacts 15 and 16 These bankcontacts, though norma ly cross-connectedsto the line conductors 2i and 22, are now cross-connected'to the trailie ringer TR. 'At the end of the d ling period, the connector functions toyproyect ringing current over the tWO'SlClGS oi the'line in series across which the frequency relay is now bridged. Frequency relay 32 operates responsive thereto, closing an initial energ1zing circuit for relay 31 which in turn operates and initiates relay operations in the trunk circuit TC that ell cct the lighting of lamp L. lVhcn the operator answers the call by 111' serting the plug of a cord, plug P for example, into the jack J, relay 51 operates and at armature 57 places ground potential on the junction point of resistances R and It via armatures 64 and Since the operating winding of the r ng cut-otl' relay l connected to battery, this relay immediately operates over a circuit similar to that over which the relay l in the previously described connection operated. Relay l in operating, cuts oil the ring and bridges the back-bridge relay 2 across the talking conductors. T he back-bridge rclay 2 does not operate, however, since its lower winding is new short circuit d by rca son of the ground potential at the midpoint of the bridge across the conductors 71 and 74-. Relay 51 in operating also opens the circuit of relay 54. A short time after its circuit is opened, relay 54 releases its armatures and as previously described connects battery to the midpoint of the bridge across the conductors 7i and H. Bach-bridge relay 2 does not operate because now its upper winding is short circuited. Relay 54, in rel-easing its armature (35, also opens the circuit of relay 58. A short time after its circuit is opened, r ay 53 deencrgizes and disconnects battery potential from the midpoint of the lnidge across conductors 71 and 74. As previously described, the back-oridgc relay 2 is not onergized in series with both resistance: ll and R and both windings of the impedance 56 suilicicntly to operate. Again, since relay 2 is prevented from operating, the normal current flow supplied to the calling line through the windings oi the line relay 3 is not rcversed, and consequently tl e calling subscribers meter is not operated.

From the foregoing description, it is seen that a trunk circuit for an intcrceptin trunk is provided which contains means for operating the ring cut-otl relay in the connector switch irrespective of the side of the line to which its operating winding may be connected, or to wriat pole of the battery this winding may be connected, and prevents the operation of the back-bridge relay of the connector used so that the subscribers meter will not be operated.

The invention, its operation and utility, having been described, what is considered new and is desired to have protected by Let ters Patent is specifically stated in the appended claims.

What is claimed is:

-1. In a telephone system, an operators position, a trunk line, means including a connector switch for extending a connection to said position, a ring cut-oti' relay in said switch, a back-bridge relay in said switch normally responsive to the operation of said ring cut-off relay, means responsive when the call is answered for operating said ring cut-oil relay and for'shunting one winding of said back-bridge relay to prevent said baclebridge relay from operating.

2. In a telephone system, an operators position, a trunk line, means including a switch for extending a connection to said position, a ring cut-oil relay in said switch, a backbridge relay in said switch normally responsive to the operation of said ring cut-oft relay, a bridge comprising two resistances connected in series across said trunk line, and means operative when the call is answered for connecting a characteristic potential to the junction of said resistances to operate said ring cut oil relay and for shunting one winding of said back-bridge relay to prevent the operation of said back-bridge relay.

3. In a telephone system, an operators position, a trunk line, means including a connector switch for extending a connection to said position, a ring cut-oil relay in said switch adapted to be connected to'either side of said trunk line, a bridge comprising two resistances connected in series across said trunk line, and means responsive to the an swering of the call for connecting a characteristic potential to the junction of said resistances to operate said ring cut-ofi' relay irrespective of the side of said trunk line to which said ring cut-off relay is connected.

4i. In a telephone system, a battery, a switch, a ring cut-oil relay in said switch connected to one pole of said battery, a second switch, a ring cut-oil relay in said second switch connected to the other pole of said battery, an operators position, a trunk line, means for extending a connection to said position via said trunk line and either of said switches, and means responsive to the answering of the call for successively connecting the poles of said battery to said trunk line to operate the ring cut-oil relay in the switch used.

5. In a telephone system, a battery, a switch, a ring cut'ofi" relay in said switch connected to one pole of said battery, a second switch, a ring cut-oil relay in said second switch connected to the other pole of said battery, an operators position, a trunk line,

means for extending a connection to said position. via said trunk line and either of said switches, a bridge across said trunk line, and means responsive to the answerlng of the call for successively connecting the poles of said battery to the midpoint of said bridge to operate the ring cut-oil relay in the switch used.

6. In a telephone system, a battery, a switch having two wipers, a ring cutoff relay in said switch connected to one pole of said battery and adapted to be connected to either of said wipers, a second switch, a ring cut-oil relay in said second switch connected to the other pole of said battery, an operators position, a trunk line, means for extending a connection to said position via said trunk line and either of said switches, a bridge across said trunk line, and means operative when the call is answered for successively connecting the poles of said battery to the midpoint of said bridge to operate the ring cut-oil relay in the switch used irrespective of the wiper or of the pole of the battery to which it is connected.

7. In a telephone system, an operators position, a signal at said position, a trunk line, a battery, a first switch, a second switch, a ring cut-oli relay in said first switch connected to one pole of said battery, a ring cut-oil relay in said second switch connected to the other pole of said battery, means for extending a connection to said position including either of said switches via said trunk, a first relay and a second relay, means responsive to the completion of said connection for successively operating said first and second relays, means controlled by said second relay for operating said signal, means operative when the call is answered for successively deactuating said first relay and said second relay to momentarily and successively connect the poles of said battery to said trunk line to operate the ring cut-ofi' relay in the switch used.

8. In a telephone system, a trunk line and means for extending a call thereover, means for answering the call, a battery and means automatically responsive when the call is answered for momentarily and successively connecting the two poles of said battery to said trunk line.

9. In a telephone system, a trunk line and means for extending a call thereover, means for answering the call, a bridge including two serially connected resistances across the conductors of said trunk, and means automatically responsive when the call is answered for momentarily and successively applying potentials to the junction of said resistances.

10. In a telephone system, a trunk line and means for extending a call thereover, means for answering the call, a battery and means automatically responsive when the call is answered for momentarily and successively connecting the poles of said battery to both conductors of said trunk line.

11. In a telephone system, a trunk line and means for extending a call thereover, means for answering the call, two slow-acting relays and means for operating them, and means responsive when the call is answered for successively deactuating said relays to momentarily and successively apply potentials to said trunk line.

12. In a telephone system, a trunk line and means for extending a call thereover, means for answering the call, a bridge including two serially connected resistances across the conductors of said trunk line, a

battery,'and means responsive when the call is'answered for momentarily and successively connecting the two poles of said battery to the junction of said resistances.

- 13. In a telephone system, a trunk line and means for extending a call thereover, means for answering the call, a' battery, two relays and, nieans for operating them, and means responsive when the call is answered for successively deactuating said relays to momentarily and successively connect the two poles of said battery to said trunk line.

1.4. In a telephone system, a trunk line and means for extending a call hereover, means tor answering the call, a bridge including two serially connected resistances across the conductorsof said trunk line, a battery, two slow-acting relays and means for operating them, and means responsive when. the. call,

is answered for successively deactuating said relays to momentarily and successively connect the poles of said battery to the junction ofsaid resistances.

15. In a telephone system, a trunk line,

means including a connector switch for extending a call'over said trunk line, means for answering the call, a ring cut-ofl' relay in said connector switch adapted to be connected to eitherv side of said trunk line, and means responsive to the answering of the call for: placing a characteristic potential on the conductors of said trunk line to operate said relay irrespective of the side of the trunk line to which said relay is connected.

16; In a telephone system, a trunk line, means including a connector switch for extending a call over said trunk line, means for answering the call, a ring cut-01f relay in said connector switch adapted to be connected toveither conductor of said trunk line, and means responsive to the answering of the call for operating said relay over the conductor ofsaid trunk line to which said relay is connected independent of the other conductor of said trunk line.

17. In a telephone system, a trunk line, means including a connector switch for extending a call over said trunk line, means for answering the call, a relay in said switch, a second relay in said switch. normally responsive to the operation of said first relay, means responsive when the call is answered foroperating said hrst'relay over one conductor of the trunk line independent of the other conductor, a resistance,'and means responsive to the operatlon of said first relay over said one conductor of the trunkfor inserting saidresistance in the circuit of said second relay to prevent the operation of said second relay.

18. In a telephone system, a battery, a switch, a ring cut-off relay in said switch connected to one pole of said battery, a second switch, 'a ring cut-off relay in said second switch connected to. the other pole of said battery, a trunk line, means including one or the other of said two switches for extending a call over said trunk line, means for answering the call, and means responsive to the answering of the call for completing a circuit over one conductor of said trunk line independent of the other conductor of said trunk line to operate the ring cut-01f relay in whichever switch is used.

19. In a telephone system, a battery, a switch having two wipers, a ring cut-01f relay in said switch connected to one pole of said battery and adapted to be connected to either of said wipers, a second switch, a ring cut-- oll' relay in said second switch connected to the other pole of said battery, an operators position, a trunk line, means-for extending a connection to said position via said trunk line and either of said switches, and means responsive to the answering of the call for completing acircuit including only one c011- ductor of the trunk to operate the ring cut-oil relay of the switch used irrespective of the wiper or of the pole of the battery to which said relay is connected.

20. In a telephone system, a trunk line, means including a connector switch for extending a call over said trunk line, means for answering the call, a back bridge relay in said switch normally responsive to the answering of the call, and means responsive when the call is answered for successively shunting the windings of said relay to prevent the operation of said relay.

In witness whereof I hereunto subscribe my name this 17th day of September, A, D., 1926 VICTOR S. THARP. 

